{"id":47119,"date":"2024-08-28T11:59:17","date_gmt":"2024-08-28T11:59:17","guid":{"rendered":"https:\/\/ubuntuhandbook.org\/?p=47119"},"modified":"2024-08-28T11:59:17","modified_gmt":"2024-08-28T11:59:17","slug":"enable-zram-ubuntu","status":"publish","type":"post","link":"https:\/\/ubuntuhandbook.org\/index.php\/2024\/08\/enable-zram-ubuntu\/","title":{"rendered":"Enable Zram in Ubuntu for Better Performance on Limited RAM"},"content":{"rendered":"

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This is a step by step tutorial shows how to enable zram Kernel module and use as Swap device for better system performance in Ubuntu 24.04 PC\/laptop with limited RAM.<\/p>\n

As you may know, Ubuntu usually includes a swap space. It works like MS Windows’ “virtual memory”, that uses the hard disk for additional memory when there is not enough physical RAM for all tasks request.<\/p>\n

Swap on disk however is slow, which will slow down the overall system performance. So, Linux introduced “zram” and “zswap” kernel modules to improve performance for computers with small amount of RAM.<\/p>\n

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Instead of using Swap on disk, zram<\/b> creates block device (use no memory initially, and grow or shrink dynamically) in RAM that can use as Swap space. It compresses the data that are going to swap out, then moves into the block device. In the case, it uses less physical memory for more data, while keeps system running faster.<\/p>\n

I’ve written about how to enable zswap in Ubuntu<\/a> to do the similar job, by providing a compressed RAM cache for swap pages. Here I’m going to show you how to use zram instead, which is enabled by default in Fedora and Pop!_OS.<\/p>\n

NOTE 1: If you have a plenty of RAM that rarely uses swap space, or you’re CPU-bound, then stay away from zram or zswap, because they consume more CPU for compressing\/decompressing.<\/b><\/p>\n

NOTE 2: zram will prevent hibernation for working properly! Use zswap instead, if you need sleep to disk.<\/b><\/p>\n

Disable zswap (if enabled)<\/h3>\n

Zswap will prevent zram from being used effectively. If you have it enabled in your Ubuntu machine, you need to disable it first for trying out zram.<\/p>\n

To check if zswap enabled<\/b>, just open terminal (Ctrl+Alt+T) and run command:<\/p>\n

systool -v -m zswap<\/pre>\n
Run sudo apt install sysfsutils<\/code> if command not found.<\/i> In the output, “enabled = “N”” means the feature is not enabled.<\/p>\n
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If it said “enabled = “Y””, then you may run the command below to disable zswap at run-time<\/b> (works until reboot):<\/p>\n
echo 0 | sudo tee \/sys\/module\/zswap\/parameters\/enabled<\/pre>\n
NOTE: According to the Kernel doc<\/a>, the data in zswap will NOT be freed immediately. You need to wait until they are either invalidated or faulted back into memory, or manually swapoff<\/code> the swap and swapon<\/code> (if need) again.<\/p>\n
If you want to disable zswap permanently, then try editing Grub boot-loader, and delete the kernel parameters for zswap (if any).<\/p>\n
sudo nano \/etc\/default\/grub<\/pre>\n
Delete zswap.enabled=1<\/code> from “GRUB_CMDLINE_LINUX_DEFAULT”, and, finally run sudo update-grub<\/code> to apply changes.<\/p>\n
Option 1: Enable Zram at Run-Time<\/h3>\n
To try out the kernel module at run-time, until system reboot or you manually disable it, just do steps below to manually load the module and set up for swap space.<\/p>\n
1.<\/b> First, press Ctrl+Alt+T<\/code> on keyboard to open up a terminal window. Then, run command:<\/p>\n
sudo modprobe zram<\/pre>\n
The command loads the zram module and creates a single block device in RAM. While, all the config files are\u00a0stored in \/sys\/block\/zram0<\/code> directory.<\/p>\n
Tips:<\/b> If want, you may create multiple zram block devices in RAM. For example, run sudo modprobe zram num_devices=4<\/code> will create 4, while the config files are located in \/sys\/block\/zram{0, 1, 2, 3}.<\/p>\n
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2.<\/b> As you can see in the last screenshot, the zram block device include many config files under \/sys\/block\/zram0<\/code>. They include:<\/p>\n